Current methods of measuring the torque applied to an automotive steering shaft are of the compliant kind and are typically accomplished by use of a torsion bar as part of the shaft, joining an upper and lower section thereof. The torsion bar is made of material with known mechanical properties and hence has known compliance. Thus, the applied torque can be calculated from a measured angular displacement, Δθ, of the torsion bar (usually in the range of plus or minus a few degrees). The calculated torque is applied to a controller which then directs an electric steering torque assist motor to provide assist torque to the steering shaft.
However, this method introduces additional compliance into the control system—an undesirable parameter affecting the speed of response and the feel of the steering action. This method also suffers from the added expense of additional parts and the fabrication thereof. It is advantageous to provide a simplified torque sensor for direct sensing of the torque applied to a shaft to which the sensor is connected. In particular it is desirable to provide a faster and more accurate non-compliant measure of the torque applied to the shaft by the driver.